1. Field of the Invention
The present invention relates to the cellular phone and the operational mode switching method of a cellular phone.
2. Description of the Related Art
In a portable personal computer and the like, power consumption is reduced by switching the computer from a normal operational mode to a suspension mode and suspending the operation of a central processing unit (CPU) and devices while a user is not operating keys.
In the suspension mode, by storing in memory the operational information of the computer immediately before the power supply is switched off and continuing to supply the memory with power, the state immediately before the computer is switched to the suspension mode can be reproduced when power is switched on next time.
In computer equipment with such a suspension mode, a variety of technologies for reducing the power consumption of equipment are proposed.
For example, Patent Reference 1 discloses a technology for reducing wasteful power consumption by performing no suspension process in a portable personal computer provided with a main battery and a sub-battery if the main battery is disconnected.
Patent Reference 2 discloses a technology in which a user arbitrarily changes the switching order even if a plurality of power saving modes are set to be switched step by step by the operating system.
Patent Reference 3 discloses a technology for storing the contents of the main memory on a HDD or the like and switching the suspension mode to a hibernation mode if the built-in battery enters a low power state or the supply of external power is suspended when a computer system is in suspension mode.
With improvements of the function of cellular phones, the time needed to power up has increases as a high-performance operating system and multi-task application must be started, a variety of setting data must be read, and similarly when the power is switched on. Therefore, even when the power is switched on, a cellular phone cannot be used immediately, which is an inconvenience.
In order to solve the above-mentioned problem, it can be considered that a cellular phone is provided with a suspension mode. However, in the case of a cellular phone, since the remaining stored charge drops quickly, communication is made impossible. Therefore, the suspension function of a portable computer cannot be applied without any modifications.    Patent Reference 1: Japanese Patent Application No. Hei 9-185436    Patent Reference 2: Japanese Patent Application No. 2001-222346    Patent Reference 3: Japanese Patent Application No. Hei 11-194846    Patent Reference 4: Japanese Patent Application No. 2002-163032